1. Field of the Invention
The present invention relates to a machine tool, and more particularly to removal of chips produced in the machine tool by machining a workpiece.
2. Description of the Related Art
In a machine tool, large amounts of chips are produced and deposited inside a splash guard when a workpiece is machined by means of a tool. If the deposited chips are left as they are, they may hinder the operations of drive systems for a table, saddle, etc. or retard the flow of machining fluid (coolant). It is necessary, therefore, to efficiently discharge the chips from the machine lest they deposit, so that various methods are proposed for chip discharge.
Roughly, there are two types of methods for discharging the chips from the machine.                A method in which the chips are discharged from the machine by means of a chip conveyor or the like.        A method in which the chips are discharged from the machine with cutting fluid (machining fluid).        
As an example of the former method, there is known a method in which a through groove is provided under a machining region, for example, the conveyor is housed in the through groove, and the chips produced by machining are guided onto the conveyor in the through groove and discharged from the machine by the conveyor (see JP 60-175541U, JP 10-180585A and 2002-326137A).
As the latter method in which the chips are discharged from the machine with the cutting fluid, there is conventionally known an example such as the one shown in FIGS. 2a and 2b. The prior art example shown in FIGS. 2a and 2b is a case that is applied to a machining center.
FIG. 2a is a front view, and FIG. 2b is a schematic sectional view taken along line A-A of FIG. 2a without illustration of a table, a guide mechanism, etc.
A table 7 is set on the bed 3 with a guide mechanism 6 between them. A column 8 for supporting a spindle 9 is disposed behind the bed 3. A splash guard 1 is provided covering the front part and two opposite side parts of the bed 3. The splash guard 1 has a bottom portion, from which the bed 3 protrudes upward. Specifically, the splash guard 1 is constructed in a manner such that its bottom portion is formed in close contact with the front part and the two side parts of the projecting bed 3 and that a vertical wall portion is then formed continuously with the bottom portion. At the bottom portion of the splash guard 1 that surrounds the bed 3, a groove 2 is formed extending continuously along its front part and two side parts. A bottom portion of this groove is formed having a downward slope such that it is higher at the front part of the machine than at the rear part. The wall portion of the splash guard 1 that is continuous with the groove 2 is inclined toward the groove.
Further, pipes 5 are arranged extending from a coolant tank 4 at the rear part of the machine to the front part, and nozzles 5a are attached individually to the respective distal ends of the pipes. The cutting fluid (coolant) that is drawn from the coolant tank 4 by a pump (not shown) flows through the pipes 5 and is jetted out from the nozzles 5a toward the groove 2. The cutting fluid flows along the groove 2, as indicated by arrows Q, and is recovered into the coolant tank 4.
In cutting the workpiece set on the table 7 by means of the tool mounted on the spindle 9, the cutting fluid (coolant) drawn from the coolant tank 4 by a pump (not shown) is jetted out from a nozzle (not shown) into a machining region, whereby the chips are guided into the groove 2. The chips that are dropped into the groove 2 are spouted from the nozzles 5a, swept away into the coolant tank 4 by the cutting fluid that flows along the slope of the bottom portion of the groove 2 from the front part toward the rear part, as indicated by the arrows Q, and separated from the cutting fluid.
Besides the example shown in FIGS. 2a and 2b, there is another known method in which chips are discharged from the machine with cutting fluid (see JP 2-35634U and JP 2001-87964A). In this method, a bed on which a table is set is provided with a hole, chips that are produced as a workpiece mounted on the table is machined are guided into the hole by cutting fluid and dropped downward, and the dropped chips are taken out manually or by means of a conveyor.
According to the above method in which the chips are discharged from the machine by means of the chip conveyor or the like, however, the chip conveyor or some other discharge means must be provided only for chip discharge, thus entailing an increase in cost. Further, there is a problem that a small machine tool cannot secure an internal space in which the conveyor or the like can be set.
On the other hand, the latter method in which the chips are removed with only the cutting fluid requires a pump, pipes, hoses, etc. as essential parts, so that it is also advantageous in installation space. In the prior art example shown in FIGS. 2a and 2b, however, the pipes must be set extending up to the front part of the machine in order to run the cutting fluid from the front part, so that the interior of the machine is complicated, and the pipes sometimes may constitute starting points for undesirable chip deposits.
According to the method in which the chips are removed by being dropped into the hole in the bed, on the other hand, the hole must be bored in the bed, and some means is required to recover the chips that are dropped under the bed.